I'm not sure there is an alternative - xinetd is deprecated and systemd socket activated services are the modern replacement.
You have suggested we "Proposition: remove timestamp from parametrization for calling mariadbcheck@ service." but I cannot see a way to do that with systemd.socket.
This will happen in more places, I see Ironic starting to use socket activated services for tftp which will behave in exactly the same way.
I'm not sure there is an alternative - xinetd is deprecated and systemd socket activated services are the modern replacement.
You have suggested we "Proposition: remove timestamp from parametrization for calling mariadbcheck@ service." but I cannot see a way to do that with systemd.socket.
This will happen in more places, I see Ironic starting to use socket activated services for tftp which will behave in exactly the same way.